I completely agree with your perception (I am 64). But my preferred explanation is simply "logarithmic compression." When we were 5, the kindie year represented a 20% increase in our time on earth, and even greater fraction of the time of which we had fair conscious awareness. My 64th year (my current one) is only 1/64 = 1.7% increase in my lifetime stock of experiences. Assume that one's perception of elapsed time is a function of the rate of new sensations per unit of time. The conclusion is that the older we are, the more time flies. This is a sobering fact, given my age. It means that the remaining 15-20 years of my life, will go by fairly quickly.

Here are a few you may enjoy:
YOU MIGHT BE A PHYSICS MAJOR...
if you have no life - and you can PROVE it mathematically.
if you enjoy pain.
if you know vector calculus but you can't remember how to do long division.
if you chuckle...